Method and system for alternator thermal protection

Abstract

A system (for controlling cooling of an alternator) comprises a control system, an alternator, and a blower fan, the alternator having a stator and a rotor. The control system is adapted to estimate one or more temperatures of the stator and/or rotor of the alternator using a thermal model. The control system is also adapted to control the blower fan to cool the alternator by providing a specified amount of air flow across the stator and rotor of the alternator, based on the estimated one or more temperatures of the stator and/or rotor.

The invention claimed is: 
     
       1. A system comprising:
 an alternator including a stator and a rotor; and 
 a blower unit, comprising:
 a control system; and 
 a blower fan integrated together with the control system to form the blower unit, wherein the blower unit is configured to estimate one or more temperatures of at least one of the stator or rotor of the alternator using a thermal model and to control the blower fan to cool the alternator by providing a specified amount of air flow across at least one of the stator or rotor of the alternator based on the one or more temperatures that are estimated. 
 
 
     
     
       2. The system of  claim 1 , wherein the control system is configured to estimate the one or more temperatures of the at least one of the stator or rotor of the alternator using nodal temperature equations within the alternator as a function of time. 
     
     
       3. The system of  claim 1 , wherein the thermal model of the alternator comprises plural thermal elements that are linked together to form a network of nodes and thermal resistances. 
     
     
       4. The system of  claim 1 , wherein the control system is configured to generate an air flow request for controlling the blower fan based on the temperatures that are estimated, said temperatures comprising nodal temperatures within the alternator. 
     
     
       5. The system of  claim 1 , wherein source terms of the thermal model of the alternator comprise losses of the alternator. 
     
     
       6. The system of  claim 1 , wherein the alternator is a salient pole alternator. 
     
     
       7. A vehicle comprising:
 a support structure; and 
 the system of  claim 1  attached to the support structure. 
 
     
     
       8. The vehicle of  claim 7 , wherein the one or more temperatures that are estimated comprise plural temperatures of the stator and the rotor of the alternator. 
     
     
       9. The vehicle of  claim 7 , wherein the thermal model of the alternator comprises plural thermal elements that are linked together to form a network of nodes and thermal resistances. 
     
     
       10. The vehicle of  claim 7 , wherein the thermal model of the alternator comprises an air flow distribution for the stator of the alternator and another air flow distribution for the rotor of the alternator. 
     
     
       11. The vehicle of  claim 7 , wherein the vehicle is an off-highway vehicle further comprising an engine attached to the support structure, and wherein the engine is configured to power the alternator for generating electricity for propelling the off-highway vehicle. 
     
     
       12. The system of  claim 1  wherein the control system is not a vehicle controller configured to control vehicle movement. 
     
     
       13. A method of cooling an alternator, comprising:
 deriving steady state temperature equations of the alternator using a controller, wherein the controller models the alternator as a thermal network that includes nodes; 
 calculating thermal resistances using heat coefficients and an air flow distribution within the alternator; 
 determining losses of the alternator; 
 deriving nodal temperatures within a stator and a rotor of the alternator using the steady 
 state temperature equations, thermal resistances, and losses of the alternator; and controlling cooling of the alternator based at least in part on the nodal temperatures. 
 
     
     
       14. The method of  claim 13 , wherein the steady state temperature equations are derived each time operating conditions of the alternator change. 
     
     
       15. The method of  claim 13 , wherein the thermal resistances are convective resistances between the nodes of the thermal network. 
     
     
       16. The method of  claim 13 , wherein the losses of the alternator are modeled in the thermal network as source terms. 
     
     
       17. The method of  claim 13 , wherein the thermal network includes capacitances assigned to each node, such that the capacitances account for thermal storage during operation of the alternator. 
     
     
       18. The method of  claim 13 , wherein the heat transfer coefficients relate to convective heat transfer from surfaces within the alternator. 
     
     
       19. The method of  claim 13 , wherein the step of controlling cooling of the alternator comprises generating an air flow request using the nodal temperatures within the stator and the rotor of the alternator. 
     
     
       20. The method of  claim 13 , further comprising:
 determining an actual temperature from the nodal temperatures within the stator and the rotor of the alternator; and 
 comparing the actual temperature to a desired temperature for the alternator; wherein the step of controlling cooling of the alternator comprises:
 generating a blower speed request to increase a blower speed when the actual temperature is higher than the desired temperature; and 
 generating an air flow request to decrease a blower speed when the actual temperature is lower than the desired temperature. 
 
 
     
     
       21. A system comprising:
 an alternator including a stator and a rotor; 
 a control system configured to estimate one or more temperatures of at least one of the stator or rotor of the alternator using a thermal model,
 wherein the control system is configured to estimate the one or more temperatures as one or more nodal temperatures within the alternator that are calculated as a function of time using the thermal model, the thermal model comprising at least one of a heat transfer coefficient between a stator and a rotor vent ducts and cooling air, a heat transfer coefficient between the stator and rotor and an air gap, a heat transfer coefficient between stator end windings and an end-cap air, a heat transfer coefficient from a pole face, or a heat transfer coefficient from a field winding; and 
 
 a blower fan, wherein the control system is configured to control the blower fan to cool the alternator by providing a specified amount of air flow across at least one of the stator or rotor of the alternator based on the one or more temperatures that are estimated. 
 
     
     
       22. A vehicle comprising:
 a support structure; and 
 a system attached to the support structure, the system comprising:
 an alternator including a stator and a rotor; 
 a control system configured to estimate one or more temperatures of at least one of the stator or rotor of the alternator using a thermal model,
 wherein the thermal model of the alternator comprises plural thermal elements that are linked together to form a network of nodes and thermal resistances, and wherein the network includes capacitances assigned to each node, such that the capacitances account for thermal storage during operation of the alternator; and 
 
 a blower fan, wherein the control system is configured to control the blower fan to cool the alternator by providing a specified amount of air flow across at least one of the stator or rotor of the alternator based on the one or more temperatures that are estimated. 
 
 
     
     
       23. A method of cooling an alternator, comprising:
 with a control system, estimating one or more temperatures of at least one of a stator or a rotor of an alternator using a thermal model; and 
 with the control system, controlling a blower fan to cool the alternator by providing a specified amount of air flow across at least one of the stator or rotor of the alternator based on the one or more temperatures that are estimated, wherein the blower fan is integrated together with the control system to form a blower unit. 
 
     
     
       24. The method of  claim 23  wherein the control system is not a vehicle controller configured to control vehicle movement.